Countess Luann de Lesseps was wary at dinner at the new Heath restaurant, located in the McKittrick Hotel on West 27th Street, when she was presented with a mysterious key. The “Real Housewives of New York City” star was told it would unlock a private room that was down a hallway behind the bar.

But she quickly returned to her table, having never opened the door. “I’m scared,” she explained.

The restaurant is an interactive offshoot of “Sleep No More,” the theatrical production loosely based on “Macbeth,” in which the audience wanders from room to room as 26 actors perform various scenes.

The Heath, which evokes a ’40s-era supper club complete with jazz band, featured similar surprises on Tuesday night for a crowd that included Guillermo Diaz from ABC’s “Scandal,” Danielle Brooks from “Orange is the New Black,” Mae Whitman from “Parenthood” and Laura Osnes, who stars as Cinderella on Broadway. Andrew Dost and Jack Antonoff of the pop band Fun. were also in the house.

Producer Randy Weiner arrived at the restaurant straight from the Diamond Horseshoe, the club under the Paramount Hotel that has been closed since 1951.

Developer Aby Rosen is reopening the club next month with the help of Weiner and The Box owner Simon Hammerstein. Expect dancers, illusionists, contortionists, clowns and “food performance” art by Jennifer Rubell.